#encoding: utf-8
import sys

def eva(name):
	with open(name, "r") as fp:
		n, pc = 0, 0
		for li in fp:
			n += 1
			vals = li.split()
			t1 = float(vals[0])
			t2 = float(vals[1])
			pc += (t2 - t1) / t1) * 100
		print("overhead", pc / n)


def main():
	if len(sys.argv) < 2:
		print("usage: eva file")
		return
	eva1(sys.argv[1])

if __name__ == "__main__":
	main()
